#include <stdio.h>
#include <math.h>

int main()
{
  int i, n;
  scanf("%d", &n);
  for (i = 2; i < sqrt(n); i++)
  {
    if (n % i == 0)
      break;
  }
  if (i > sqrt(n))
    printf("This is a prime.");
  else
    printf("This is not a prime.");
  return 0;
}